A common form of valve closure, known as an A-type valve, is often used with beer kegs. A single spring-loaded annular valve element controls two ports. When engaged with a suitable valve-operating member, gas can be fed into the container past the outer periphery of the valve element while beer simultaneously flows out of the container past the inner periphery of the element.
Other forms of valve closure may also be used with beer kegs. For example, in S-type valves the two ports are controlled by inner and outer concentric valve members which are spring-loaded to close inner and outer passages within the valve closure. Generally the valve members are operated by respective spring elements, although the valve members may be cascaded such that one spring-loaded valve member causes closure of the other.
Traditional valve closures are designed to have a long working life. They are predominantly metal and are relatively expensive. On the other hand, single-use beer kegs are becoming more popular because they minimise the environmental cost of transporting heavy beer kegs over long distances. Stripping down a beer keg to remove different components is a labour-intensive process, and ideally the entire beer keg should be capable of being recycled after a single use with a minimum amount of manual intervention.
An objective of the present invention is to provide a valve closure which can be formed of inexpensive materials and which can be recycled without separation of its various components but which nevertheless performs the necessary sealing functions effectively and reliably.